Method for preparing stable aqueous dispersions of ionomer resins

ABSTRACT

A process is disclosed for preparing stable aqueous dispersions of ionomer resins. Intimate fusion blends of 100 parts of an ionomer resin and about 5 to 900 parts of an alkenyl succinic anhydride (the alkenyl group containing about 16 to 52 carbon atoms) are heated and stirred with an aqueous alkaline medium.

This is a division of application Ser. No. 209,812 filed Nov. 24, 1980,now U.S. Pat. No. 4,324,872.

BACKGROUND OF THE INVENTION

Metal salts of copolymers of ethylene with acrylic or methacrylic acidare described in the art as ionomer resins. While such resins have anumber of desirable properties, their use is somewhat limited byprocessing difficulties. In a specific area of application, the ionomerresins are used as coating resins. Many attempts have been made toprepare aqueous dispersions of ionomer resins for use as coatingcompositions. Considerable difficulties are encountered in making suchaqueous dispersions. Accordingly, there is a need in the art forformulating products containing ionomer resins which are easier toprocess.

SUMMARY OF THE INVENTION

The applicant has discovered novel extrudable, alkali-soluble polymericcompositions consisting of an intimate fusion blend of:

(1) 100 parts by weight of an ionomer resin and

(2) About 5 to 900 parts by weight of an alkenyl succinic anhydride.

The alkenyl group attached to the succinic anhydride will contain about16-52 carbon atoms. In addition to being readily extrudable, suchcompositions can be dispersed in aqueous alkaline media to form usefulaqueous dispersions for use in preparing coated articles.

DETAILED DESCRIPTION OF THE INVENTION

The compositions of the invention contain about 5 to 900 parts of thealkenyl succinic anhydride (hereinafter sometimes referred to as ASA forbrevity of expression) per 100 parts of ionomer resin. The compositionsof the invention fall into two fairly distinct classes. The first classcontains from about 5 to 100 parts, preferably about 15 to 100 parts,more especially about 20 to 80 parts and ideally about 25 to 50 parts ofASA per 100 parts of ionomer resin. This first class of resins hasexcellent physical properties approaching those of the ionomer resinsthemselves. The ASA functions to improve the processing characteristicsand particularly the dispersibility of the ionomer resins in aqueousalkaline media. The second class of composition contains from 100 to 900parts of ASA per 100 parts of the ionomer resin. In this class ofmaterials, the ionomer resin in effect functions to convert the ASA froma nonresinous material into a low cost, film forming composition.

In the preferred embodiments of the invention, the two named componentsconstitute the entire composition. Optionally, however, the compositionsmay contain up to about 20 weight % of additional components, providedthat such optional components do not alter the alkali dispersibility ofthe compositions of the invention as described infra. An antioxidant ofthe type conventionally employed with ethylene polymers desirably isincluded in the compositions.

The ionomer resin included in the blends will be a metal salt of anethylene-acid copolymer, specifically a copolymer of ethylene andacrylic or methacrylic acid having an acid content of about 1-10 mol %.The ethylene-acid copolymer, in addition to the polymerized ethylene andacid moiety, may contain up to about 10 mol % of additional polymerizedmonomer moieties such as vinyl acetate, alkyl acrylates, alkylmethacrylates, acrylamide, methacrylamide, and the like. The cationemployed in the salt preferably is monovalent such as alkali metal ions,e.g., sodium and potassium ions. Certain polyvalent metal ions can beemployed in certain circumstances, e.g., zinc ions. In most cases, it ispreferred to employ the metal cation in an amount that is less thanstoichiometrically equivalent to the carboxylic acid groups of theethylene-acid copolymer. Where the preferred quantity of the metalcation is employed, the ionomers can be viewed as being terpolymerscontaining polymerized ethylene, a salt of the polymerised acid, and thefree polymerized acid.

The composition of the ionomer, including its molecular weight, mol %acid content, and cation content, should be adjusted so that the ionomerhas a high load melt index (ASTM 1238-70, Condition F) of at least about1.0. It's feasible to employ ionomers having a normal load melt index(ASTM 1238-70, Condition E) as high as about 50. The preferred ionomerresins will have a normal load melt index in a range of about 1 to 20.Suitable ionomers can be prepared by methods reported in the prior art.See U.S. Pat. No. 3,264,272; U.S. Pat. No. 3,485,785; and U.S. Pat. No.3,970,626 whose descriptions are incorporated herein by reference. Onemethod consists of preparing an ethylene-acrylic (or methacrylic) acidcopolymer and reacting it with sodium hydroxide to convert the desiredpercentage of carboxylic acid groups to sodium carboxylate groups.Another method involves saponifying an ethylene-alkyl acrylate (ormethacrylate) copolymer with an aqueous alkali metal hydroxide solutionto form a stable aqueous emulsion of the alkali metal salt of anethylene-acrylic (or methacrylic) acid copolymer. Such emulsion can becoagulated with carbon dioxide as disclosed in U.S. Pat. No. 3,553,178to recover the alkali metal salt in a solid form.

The alkenyl succinic anhydride employed in the compositions of theinvention are known compounds of the type described in U.S. Pat. No.4,158,664, whose descriptions are incorporated herein by reference.These compounds are prepared by heating a high molecular weightalpha-olefin containing about 16 or more carbon atoms with maleicanhydride. Their structure is shown below: ##STR1## In the aboveformula, R is an alkyl group containing about 13 to 49 and preferably 15to 39 carbon atoms. Frequently these compounds are prepared from amixture of alpha-olefins in which each component contains a minimum ofabout 16 carbon atoms. In this event, R can be expressed as an averagevalue. The color of the compounds can be improved (lightened) bytreatment with water.

The compositions are prepared by malaxating the ionomer resin and theASA employing conventional equipment such as rubber mills, Banburymixers, compounding extruders, Brabender Plasticorders and the like. Itis preferred practice to first flux the ionomer resin, then add the ASA,and then continue the mixing until a uniform, intimate dispersion of thetwo components is obtained.

The compositions, particularly those containing less than 100 parts ofASA per 100 parts of ionomer resin, have properties and characteristicssimilar to the ionomer resin contained therein. They have much highermelt indexes than the ionomer resins and are easily fabricated intocoatings and films. They are quite transparent and have good adhesion topaper, aluminum foil, copper foil, ethylene polymers to both the lowdensity and high density types, and isotactic propylene polymers.Accordingly, the compositions are well suited for use in the manufactureof laminated sheet constructions by conventional laminating techniques.The compositions have excellent resistance to a number of solvents,including particularly natural fats, and good vapor barrier properties.The adhesion of such compositions to the principal thermoplastic resinsof commercial interest (as measured by peel strength discussed infra) isadequate for most purposes. Thus, they are well suited for use in themanufacture of composite thermoplastic film constructions by coextrusiontechniques of the type shown in U.S. Pat. No. 4,152,387, thedescriptions of which are incorporated herein by reference.

The compositions of the invention can be readily dispersed in aqueousalkaline media to prepare low viscosity, compositionally uniformdispersions. To prepare such dispersions, at least 10 parts by weight ofthe compositions and 100 parts by weight of an aqueous alkaline mediumare heated and stirred for a time sufficient to disperse the solids ofthe composition throughout the aqueous medium to form a low viscosity,compositionally uniform dispersion. To prepare such compositions, it ispreferred practice to change the aqueous alkaline medium to a vesselprovided with a stirrer capable of providing intense agitation. Thealkaline medium is heated to an elevated temperature of at least about75° C. Finely divided particles of the fusion blend of the ionomer andthe ASA then are added slowly in small increments. The quantity ofalkali included in the alkaline medium will be sufficient to provide pHof at least 9, and preferably at least about 10 in the final dispersion.The alkali employed can be either an inorganic alkali, such as an alkalimetal hydroxide, e.g., sodium hydroxide or potassium hydroxide; or anitrogenous base such as ammonium hydroxide or an amine such astriethanolamine, 2-dimethylaminoethanol, 2-amino-2-methyl propanol, etc.

When the blend to be dispersed contains less than about 15 parts of ASAper 100 parts of ionomer resin, somewhat more rigorous condition may berequired to form the aqueous alkaline dispersions. Specifically, highertemperatures may be required. This, in turn, may require thatautogeneous pressures be employed in sealed reactors.

The following examples are set forth to illustrate more clearly theprinciple and practice of the invention to those skilled in the art.Where parts or percentages are mentioned, they are parts or percentageson a weight basis unless otherwise noted. The materials employed in theexamples are described below.

Ionomer resin A was a commercial product sold under the designationSurlyn 1605. This product is reported by the manufacturer to be a sodiumsalt of an ethylene-methacrylic acid copolymer having a melt index ofabout 2.8.

Ionomer resin B was a commercial product sold under the designationSurlyn 1555. This product is reported by the manufacturer to be a sodiumsalt of an ethylenemethacrylic acid copolymer having a melt index ofabout 14.

Ionomer resin C was a commercial product sold under the designationSurlyn 1652. This product is reported by the manufacturer to be a zincsalt of an ethylenemethacrylic acid copolymer having a melt index ofabout 5.

Ionomer resin D was a commercial product sold under the designationSurlyn 1605. This product is reported by the manufacturer to be a sodiumsalt of an ethylenemethacrylic acid copolymer having a melt index ofabout 14.

ASA-A was prepared by condensing an alpha-olefin with maleic anhydrideby the procedure described in U.S. Pat. No. 4,158,664. The alpha-olefinemployed was a mixture in which the lowest molecular weight componentcontained 30 carbon atoms. The average number of carbon atoms in thefraction was 38.

ASA-B was prepared by condensing a C-18 alpha-olefin with meleicanhydride by the procedure described in U.S. Pat. No. 4,158,664.

ASA-C was prepared by condensing a C-12 alpha-olefin with maleicanhydride by the procedure described in U.S. Pat. No. 4,158,664.

EXAMPLE 1

A series of intimate fusion blends of the ionomer resins and the alkenylsuccinic anhydrides previously described were prepared. These blendswere prepared employing a laboratory-size Brabender Plasticorder havinga 400-gram mixing head, with the torque-balance arm being set at 3000meter-grams. The Plasticorder mixing head was heated to a temperature ofabout 200° C., at which time the unit was started employing a bladespeed of 20 rpm. The ionomer resin particles were added in smallincrements until approximately two-thirds of the desired ionomer resinwas fluxed in the apparatus. The ASA then was added in small incrementsuntil the entire mass was fluxed. The balance of the ionomer resin thenwas added and the mixing was continued until the entire mass was fluxedand intimately mixed. The mixture then was cooled and chopped into smallparticles.

The chopped particles were intimately mixed with powdered dry ice andpermitted to stand for approximately 20 minutes. The chilled particleswhich still contained a quantity of dry ice were charged to a heavy dutyWiley mill fitted with a 3 mm screen. The finely powdered material wasrecovered and used for testing purposes.

The blends prepared, the melt indexes of the blends, and thestress-strain properties of the materials are shown in Table I. Thestress-strain properties of the ionomer resins employed are set forthfor comparison purposes.

                                      TABLE I                                     __________________________________________________________________________    Blend                               Control                                                                            Control                                                                            Control                                                                            Control                    Composition                                                                            A  B  C  D  E  F  G  H  J  A    B    C    D                          __________________________________________________________________________    Component                                                                     Ionomer Resin A                                                                        100                                                                              -- -- -- 100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100  --   --   --                         Ionomer Resin B                                                                        -- 100                                                                              -- -- -- -- -- -- -- --   100  --   --                         Ionomer Resin C                                                                        -- -- 100                                                                              -- -- -- -- -- -- --   --   100  --                         Ionomer Resin D                                                                        -- -- -- 100                                                                              -- -- -- -- -- --   --   --   100                        ASA - A  33 33 33 33 18 54 82 -- -- --   --   --   --                         ASA - B  -- -- -- -- -- -- -- 18 -- --   --   --   --                         ASA - C  -- -- -- -- -- -- -- -- 18 --   --   --   --                         Melt Index                                                                             74 244                                                                              62 84 14 183                                                                              750                                                                              30 56 3.5  10.4 4.0  21.1                       Tensile @                                                                              1990                                                                             1290                                                                             1800                                                                             1730                                                                             3290                                                                             1760                                                                             1320                                                                             2509                                                                             2760                                                                             4190 3270 3640 3760                       break, psi                                                                    Tensile @                                                                              1490                                                                             1080                                                                             1240                                                                             1220                                                                             1780                                                                             1360                                                                             1340                                                                             950                                                                              1100                                                                             2210 1730 1230 1670                       yield, psi                                                                    Elongation @                                                                           270                                                                              120                                                                              350                                                                              290                                                                              380                                                                              240                                                                              90 385                                                                              345                                                                              320  320  430  410                        break, %                                                                      __________________________________________________________________________

In analyzing the data, it is noted that all of the compositions havemuch higher melt indexes when the ionomer resin contained therein. Forthis reason, the compositions are much easier to extrude than is theionomer resin. Comparison of the data for Blends A, E, F, and Gindicates the manner in which properties vary as the concentration of aspecific ASA is varied with Ionomer Resin A. Comparison of the data forBlends E, H, and J indicates that varying the number of carbon atoms inthe alkenyl chain of the ASA does not have a major effect on melt indexor physical properties when the ASA is blended with Ionomer Resin A.

EXAMPLE 2

A series of aqueous alkaline dispersions were prepared from the finelydivided intimate fusion blends of the ionomer resins and ASAs preparedin Example 1. The disprsions were made in a one liter vessel fitted witha laboratory size Gifford-Woods mixer. The vessel was initially chargedwith water in the amount of approximately 500 or 600 ml and the quantityof alkali to be employed. In certain of the runs, n-butanol was includedas an auxiliary dispersing agent. The alkaline solution was heated to aminimum temperature of 75° C. At this temperature, the finely powderedblends were added slowly and the speed of the agitator was increased.The temperature was gradually increased to at least 90° C., and thepowdered blend was continually added in small increments at a ratesubstantially corresponding to the rate at which the added particleswere being dispersed.

In Table II which follows are shown the materials charged to prepare theseveral dispersions. The processing conditions are shown with therecorded time being the interval between the first addition of thepowdered blend and the conclusion of the addition. Two temperatures areshown for each run, with the lower temperature being the temperature atwhich the first addition of the blend was made and the secondtemperature being the final temperature employed in the preparation ofthe dispersion. The emulsion properties shown are the percent solids,the pH, and the dispersion's viscosity in centipoises.

                                      TABLE II                                    __________________________________________________________________________    Dispersion                                                                    Identification                                                                         DA-1                                                                              DA-2                                                                              DA-3                                                                              DB-1                                                                              DD-1                                                                              DH-1                                                                              DH-2                                                                              DE-1                                                                              DA-4                                                                              DF-1                                                                              DG-1                         __________________________________________________________________________    Charge                                                                        Blend A(1)                                                                             80  80  80  --  --  --  --  --  80  --  --                           Blend B(1)                                                                             --  --  --  80  --  --  --  --  --  --  --                           Blend D(1)                                                                             --  --  --  --  80  --  --  --  --  --  --                           Blend H(1)                                                                             --  --  --  --  --  80  80  --  --  --  --                           Blend E(1)                                                                             --  --  --  --  --  --  --  80  --  --  --                           Blend F(1)                                                                             --  --  --  --  --  --  --  --  --  80  --                           Blend G(1)                                                                             --  --  --  --  --  --  --  --  --  --  80                           NaOH     4   --  --  --  --  --  --  --  --  --  --                           KOH      --  5.6 --  --  --  --  --  --  --  --  --                           30% NH.sub.4 OH                                                                        --  --  16.2                                                                              11.2                                                                              16.2                                                                              20  28  16.2                                                                              16.2                                                                              16.2                                                                              16.2                         DMAE(2)  --  --  5.6 5.6 6.0 6   6   5.6 5.6 5.6 5.6                          n-Butanol                                                                              --  --  --  --  --  --  45  --  --  --  --                           Water    511 511 600 600 600 600 600 600 600 600 600                          Processing                                                                    Conditions                                                                    Time, hours                                                                            1.5 1.5 0.75                                                                              2.0 2.5 4.5 3.0 1.0 1.0 1.0 1.0                          Temperature, °C.                                                                75-90                                                                             75-90                                                                             90-95                                                                             90-95                                                                             85-95                                                                             90-95                                                                             90-95                                                                             90-95                                                                             90-95                                                                             90-95                                                                             90-95                        Emulsion                                                                      Properties                                                                    Solids, %                                                                              15.2                                                                              15.4                                                                              15.0                                                                              13.5                                                                              14.1                                                                              15  13.5                                                                              13.5                                                                              15.0                                                                              14.5                                                                              13.0                         pH       9.8 10.1                                                                              9.4 9.3 9.3 9.7 9.9 10.1                                                                              10.0                                                                              10.2                                                                              10.2                         Viscosity, cps                                                                         30  25  820 510 80  725 25  135 55  135 30                           __________________________________________________________________________     (1)Blend Identification shown in Table I                                      (2)DMAE = 2Dimethylaminoethanol                                          

An attempt to prepare a dispersion from 80 parts of Blend J (shown inTable I), 28 parts of 30% NH₄ OH, 6 parts of DMAE, 25 parts ofn-butanol, and 600 parts of water at a temperature range of 90°-95° C.in a 5-hour period was unsuccessful.

EXAMPLE 3

A series of coated articles were prepared by laying down coatings of theaqueous dispersions shown in Example 2 on a number of substrates,specifically, kraft paper, aluminum foil and low density polyethylenefilm.

Dispersions DE-1, DA-3, DH-1, and DH-2 were coated onto 40-pound kraftpaper which was approximately 4 mils thick. The emulsions were appliedat a level sufficient to provide a dry coating 0.5 mil thick. Thecoating was permitted to dry for several hours. The coating then wascured by heating for two minutes at 125° C. Aluminum foil 1 mil thickwas coated in the same manner as described above with respect to kraftpaper.

One mil film of low density polyethylene, the surface of which had beentreated by Corona discharge, was coated with dispersions DE-1, DA-3, andDF-1. The coating method was identical to that previously described forthe coating of kraft paper, except that final curing of the coating wascarried out by heating for two minutes at 110° C.

A first series of laminates was prepared from the coated kraft paper byplacing the coated sides of two sheets together and sealing the laminateby heating for 0.5 sec. under pressure of 40 psig at 138° C. A secondseries of laminates was prepared by placing the coated surface of onekraft sheet against the uncoated surface of a second kraft sheet andheat sealing under the conditions previously described.

Two series of laminates were prepared from the coated aluminum foil. Thefirst series was prepared by placing the two coated surfaces togetherand sealing under the same conditions employed with the kraft paperlaminates previously described. The second series was prepared byplacing the coated side of one sheet of foil against the uncoated sideof a second sheet of aluminum foil. The sealing conditions were the sameas previously described.

Two series of laminates were prepared from the film of LDPE in the samemanner as previously described, with the single exception that thesealing temperature employed was 110° C.

A final series of laminates was prepared by placing the coated surfaceof the LDPE film in contact with uncoated kraft paper and employing thesealing conditions previously described for preparing the laminates ofLDPE film.

The seal strengths of the laminates were measured by pulling thelaminates apart in an Instron machine operated at a cross-head speed of2"/minute. The seal strengths are expressed in grams/inch per width. Thedata are set forth in Table III.

                  TABLE III                                                       ______________________________________                                         Coating Dispersion                                                           Employed    DE-1     DA-3    DF-1  DH-1  DH-2                                 ______________________________________                                        Laminate                                                                      Pairs Bonded                                                                  Kraft coated/                                                                             810      858     --    362   203                                  Kraft coated                                                                  Kraft coated/                                                                 Kraft uncoated                                                                            723      680     --    --    --                                   Al. foil coated/                                                              Al. foil coated                                                                           770      588     --    203   135                                  Al. foil coated/                                                              Al. foil uncoated                                                                         135      135     --    --    --                                   LDPE coated/                                                                  LDPE coated 497      497     406   --    --                                   LDPE coated/                                                                  LDPE uncoated                                                                             135      340     135   --    --                                   LDPE coated/                                                                              <106     225     130   135   195                                  Kraft uncoated                                                                ______________________________________                                    

What is claimed:
 1. A method for preparing a stable aqueous dispersionof an ionomer resin which consists essentially of heating and stirring amixture of at least 10 parts by weight of an alkali-soluble,ionomer-containing polymeric composition and 100 parts by weight of anaqueous alkaline medium for a time sufficient to disperse the polymersolids throughout the aqueous medium and form a low viscosity,compositionally uniform dispersion; the quantity of alkali in thealkaline medium being sufficient to provide a pH of at least 9 in thefinal dispersion; said alkali-soluble, ionomer-containing polymericcomposition consisting essentially of an intimate fusion blend of;(a)100 parts by weight of an ionomer resin, and (b) about 5 to 900 parts byweight of an alkenyl succinic anhydride;said ionomer resin being a metalsalt of an ethylene-acid copolymer which is a copolymer of ethylene andacrylic or methacrylic acid having an acid content of about 1-10 mol %and having a high load melt index of at least about 1.0 and a normalload melt index of up to about 50; and said alkenyl succinic anhydridehaving the structure: ##STR2## where R is an alkyl group containingabout 13 to 49 carbon atoms.
 2. A method of claim 1 in which the alkaliconsists essentially of an alkali metal hydroxide.
 3. A method of claim1 in which the alkali consists essentially of a nitrogenous base.
 4. Amethod of claim 1 in which the alkali-soluble, ionomer-containingpolymeric composition dispersed in the aqueous alkaline medium containsabout 15 to 100 parts by weight of the alkenyl succinic anhydride.
 5. Amethod of claim 1 in which the alkali-soluble, ionomer-containingpolymeric composition dispersed in the aqueous alkaline medium containsabout 20 to 80 parts by weight of the alkenyl succinic anhydride.
 6. Amethod of claim 1 in which the R group of the alkenyl succinic anhydridecontains about 15 to 39 carbon atoms.
 7. A method of claim 4 in whichthe R group of the alkenyl succinic anhydride contains about 15 to 39carbon atoms.
 8. A method of claim 5 in which the R group of the alkenylsuccinic anhydride contains about 15 to 39 carbon atoms.
 9. A stableaqueous dispersion prepared by the method of claim 1, 2, 3, 4, 5, 6, 7,or 8.